Transformer core



June 11, 1929. J J, FRANK TRANSFORMER coma Filed Sept 4, 1928 tOP: John J. Frank, b

His Attorney. 7

Patented June 11, 1929.

UNITED STATES JOHN J. FRANK, OF PITTSFIELID, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC PATENT QFFICE.

COMPANY, A CORPORATION OF NEW YORK.

TRANSFORMER OOREL Application filed September 4, 1928. Serial No. 303,676.

My invention relates to transformer cores and more particularly to transformer cores of the air blast type. The hysteresis and eddy current lossesin the magnetic core of a transformer cause internal heating of the core and ventilating ducts are often provided in the body of such a core through which some cooling medium, such as air or oil, may flow to carry away the heat and prevent excessive temperatures. ,The general object of the invention is to provide an improved transformer core of the air blast type having a winding leg with an internal ventilating duct.

The invention will be better understood from the following description taken in connection with the accompanying drawingin which Fig. 1 is a sectional view of a horizontal core type air blast transformer having a core constructed in accordance with the invention; Fig. 2 is a perspective view of two core laminations which may be used in the core shown in Fig. 1 and Fig. 8 is a perspective view of two laminations of somewhat different construction which may be used.

Like reference characters indicate similar parts in the different figures of the drawing.

The transformer shown in Fig. 1 is of the air blast type and has a horizontal laminated core with a central winding leg 10 and two outer legs 11 and 12. lVhile this particular core is of the horizontal type, it will be apparent that the invention is not limited to cores which are arranged horizontally. The windings 13 which surround the windingleg 10 are formed of flat coils spaced apart by spacing strips 1 1. The transformer is sup ported by a closed base 15 into which air may be forced, the air then flowing up through the vertical spacesbetween the coils of the. windings 13 to cool the windings and core. A protective casing 16 with outlets 17 for the cooling air is provided over the top of the transformer.

The winding leg 10 of the core has a vertical internal ventilating duct 18 through which some of the cooling air may flow. If this ventilating duct 18 is extended entirely across the core so that it is open at its two opposite vertical edges it divides the core into two separate. sections which must be secured together by suitable heavy clamping means. Unless the vertical side edges of the duct are blocked, too, much of the air which enters the bottom of the duct will escape through the sides of the duct and be largely wasted instead of being forced straight up through the duct and through the spaces between the top horizontal portions of the coils of the windings 13. The invention provides an improved core construction having a ventilating duct which avoids these disadvantages.

The core is built up of superposed sectional layers or laminations which are interleaved and assembled into a solid three-legged horizontal type core unit with a vertical ventilating duct through the center or winding leg of the core, the vertical side edges of the duct being blocked by parts of the core structure to prevent escape of air at these places.

One way in which the laminations may be formed is shown in Fig. 2 where each lamination comprises four L-shaped sections fitted together to form the three leg portions 10, 11 and 12 and the yoke portions joining the ends of theleg portions. The sections are similarly arranged in all the laminations, but some of the laminations are reversed in position with respect to the others so that the joints are offset. The central leg portion 10 is formed of two spaced portions 19 and 20 of two of the sections, the other portions 21 and 22 of these two sections extending lateral ly into the yoke portions. The spaces 18 between the sections 19 and 20 form the corresponding duct 18 shown in Fig. 1 after the laminations are assembled. The portions 21 and 22 extend across the ends of the spaces 18 and close the opposite ends of these spaces and the opposite vertical edges of the duct 18 in the completed core. 7

In the arrangement shown in Fig. 3, each lamination is formed of a plurality of straight lamination sections. This has the advantage that the grain of the magnetic material may be parallel with the magnetic flux path in all parts of the core, but there are more joints t an in the arrangement shown in Fig. 2. The space 18, however, as in the arrangement shown in Fig. 2, is formed bythe spaced lamination sections 19 and 20 and its ends are closed by the yoke sections 21 and 22. The laminations are all similar, but some are reversed with respect to the others so that the joints are offset. 7

The invention has been explained by describing and illustrating certain forms thereof, but it will be apparent that various changes may be made Without departing from the scope of the invention as defined in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A laminated transformer core including a center Winding leg and two outer legs connected by end yokes, the Winding leg having a ventilating duct formed by spaced lainination sections, and the yoke lamination sections extending across and closing the opposite edges of said duct.

2. A laminated transformer core including a center winding leg and two outer legs connected by end yokes, the Winding leg having a ventilating duct formed by spaced lamination sections, the yoke lamination sections extending across and closing the opposite edges of said duct, and the joints in some of the yoke laniinations being ofi'set with respect to the joints in the other yoke laminations.

3. A laminated transformer core including a center Winding leg and two outer legs c011- nected by end yokes, each lamination including a Winding leg portion formed of two spaced lamination sections, and yoke sections extending across and closing the ends of the space hetween'said two spaced Winding leg sections.

In Witness whereof, I have hereunto set my hand this 29th day of August, 1928.

JOHN J. FRANK. 

